Epic! There's just no other word to describe what fans witnessed at Cal Jam '17 as Foo Fighters finished out a stellar day of music ... with a little help from their friends of course. Some you might expect as they had been on the bill earlier in the day, but others came as a surprise.

Early on in the performance, Dave Grohl invited sax legend Dave Koz and The Kills' Alison Mosshart onto the stage to perform "La Dee Da" off the new Concrete and Gold album, and both musicians shined just as much if not more onstage as they did guesting on the Foos disc. You can see footage of that performance below.

Grohl made an appearance during Liam Gallagher's set earlier in the day, so the hooded Gallagher came out for arguably the set's most "wow" moment, a performance of the Beatles' "Come Together" with Aerosmith's Joe Perry getting in on the fun. Gallagher holds up a lyric sheet during the performance. You can see footage of that above, with a little bit of Gallagher stage diving into the crowd below. Perry stuck around to play with the Foos on a performance of Aerosmith's "Draw the Line" as well, and fan-shot footage can be viewed below.

And it appears as though Grohl really did mean that Rick Astley was his "new best friend," as Astley joined the Foos at Cal Jam to do their "Never Gonna Give You Up / Smells Like Teen Spirit" mashup. Astley comes out to hype the crowd, earning a chuckle from Grohl before launching into the song.

While acts like Starcrawler and Cage the Elephant earlier in the day chose to pay tribute to the late Tom Petty with onstage covers of Petty's music, Foo Fighters did so in a more understated way. During the performance of "My Hero," Petty's face graced the background for fans to see.

The day also featured killer sets from Queens of the Stone Age, Cage the Elephant, Liam Gallagher, Royal Blood, The Struts, Bob Mould, The Kills, Fireball Ministry and many more. See some of the Foo Fighters' Cal Jam highlights above and below and stay tuned for our recap and photo gallery from the festival coming soon.